Cast-in anchors are typically considered the best option for new build projects using a RC (reinforced concrete) structure. There are several standard balcony anchors on the market which can be used, however Sapphire have developed their own because of three primary reasons;
Firstly, many of the anchors on the market fulfil the minimum L/180 structural requirements but these will often still feel ‘bouncy’. Secondly, brackets are often cast with difficulty and end up with poor setting out and alignment. Thirdly, many of the standard options available are expensive per Unit, however the glide on Cassette® system often reduces the quantity of anchors and therefore the cost of this element.
Typically, we will preassemble the connection bracket assembly offsite in CE certified production facilities. This will normally include the assembly of stubs or arms, edge shutter, thermal break and the cast in elements. These will typically be preassembled onto craneable metal stillages so that on delivery to site, they can be craned to where the RC frame contractor can set them out into the final positions. We will often provide templates to set out which enable accuracy of casting.
Whilst there are large tolerances built into standard Cassette® balconies, it is recommended that an as built survey is made of all brackets, to ensure agreed tolerances have been met, and highlight any concrete casting inaccuracies which may have occurred.
Post tension slabs seem to have become a much more common solution recently. Whilst there tends to be much less rebar used, because of the tensioning wires, the anchors are normally near identical to those used with RC frame constructions.
The positioning of the tensioning wires needs to be considered relative to the anchor positions, to ensure neither the slab strength or the balcony rigidity are compromised. Due to the critical nature of these connections, we recommend positioning the balcony anchors first. Again the simplistic nature of the cast in anchor, which doesn’t have diagonal braces between the top and bottom bolts, makes for easier casting in.